Atom-at-a-time studies

Fm, the daughter of the new element, was collected using the recoil technique, one atom at a time, and identified as Fm by their position in the cation-exchange elution curve. A half-life of 3 s was assigned to No at that time. However, it is now known that the 3 s radioactivity was No produced in the Cm ( C,4n) reaction the used target contained 20 times more Cm than Cm. No is now known to have 55 s half-life. The errors in this experiment indicate the difficulty associated with one-atom-at-a-time studies. In subsequent chemical experiments, it was found that the most stable oxidation state of element 102 in solution was 2+. The element was named nobelium after Alfred Nobel. 

SISAK for fission yield measurements. Recently the technique was successfrilly applied to one-atom-at-a-time studies of rutherfordium (Omtvedt et al. 2002, 2007). 

The study of the chemical properties of the heaviest known elements in the Periodic Table is an extremely challenging task and requires the development of unique experimental methods, but also the persistence to continuously improve all the techniques and components involved. The difficulties are numerous. First, elements at the upper end of the Periodic Table can only be artificially synthesized "one-atom-at-a-time" at heavy ion accelerators, requiring highest possible sensitivity. Second, due to the relatively short half-lives of all known transactinide nuclides, very rapid and at the same time selective and efficient separation procedures have to be developed. Finally, sophisticated detection systems are needed which allow the efficient detection of the nuclear decay of the separated species and therefore offer unequivocal proof that the observed decay signature originated indeed form a single atom of a transactinide element. 

A large variety of tools, from manual separation procedures to very sophisticated, automated computer-controlled apparatuses have been developed and are now at hand to study the chemical properties of these short-lived elements one-atom-at-a-time in the liquid phase and in the gas phase. It is demonstrated in Chapter 4 how this can be achieved, what kinds of set-ups are presently available and what the prospects are for future developments to further expand our knowledge. 

Single atom chemistry is of particular importance if only single atoms are available for chemical studies, as in the case of the heaviest elements. The short-lived isotopes of these elements can only be produced at a rate of one atom at a time, and the investigation of their chemical properties requires special considerations. 

W. W. Meinke (Ed.), Monographs on the Radiochemistry of the Elements, Subcommittee on Radiochemistry, National Academy of Sciences, National Research Council, Nuclear Science Series, NAS-NS 3001-3058, Washington, DC, 1959-1962 W, W. Meinke (Ed.), Monographs on Radiochemical Techniques, Subcommittee on Radiochemistry, National Academy of Sciences, National Research Council, Nuclear Science Series NAS-NS 3101-3120, Washington, DC, 1960-1965 I. Zvara, One Atom at a Time Chemical Studies of Transactinide Elements, in Transplutonium Elements (Eds. W. Muller, R. Lindner), North-Holland, Amsterdam, 1976 G. Herrmann, N. Trautmann, Rapid Chemical Separation Procedures, J. Radioanal. Chem. 32, 533 (1976)... 

We have recently developed the Ehrenberg idea to obtain a useful research tool, and the first tests with this equipment have given results even more interesting than we anticipated. Up to the present time it has been used in the study of clean surfaces of crystals of tungsten, inckel, and silicon and of adsorbed layers of gases upon these surfaces, only one species of gas atoms at a time. An obvious development for the near future is the extension of this work to the study of two gases simultaneously present in the apparatus, and doubtless to the conditions under which they react on the crystal surface. 

The specific problems discussed in this book require the use of fundamental concepts and equations from various fields like kinetic theory of gases, kinetics of chemical reactions, thermodynamics and mass transfer. This chapter presents some basic relationships relevant to these problems. From the very beginning, the studies of gas-phase radiochemistry of heavy metallic elements have been largely motivated by the quest for new man-made chemical elements. It necessitated experimentation with very short-lived nuclides on one-atom-at-a-time basis. We will pay much attention to this direction of research. Accordingly, we will consider microscopic pictures (at the atomic and molecular level) of the processes underlying the experimental methods and concrete techniques, and follow individual histories of the molecules. 

When studying chemical properties of TAEs on the one-atom-at-a-time (per shift, day, week or month) level - which requires not only large intellectual and material efforts but also a lot of patience - the experimenters are inevitably tempted to draw more definite and numerous conclusions than the poor statistics actually permit. It is important to be aware of this danger and pay due attention to the statistical uncertainties of the obtained data, especially when counting is not free of background. 

Zvara I (1976) One-atom-at-a-time chemical studies of transactinide elements. In Muller W, Lindner R (eds) Transplutonium elements - Proc 4th Internal transplutonium elements symposium, Baden Baden. North Holland, Amsterdam, p. 11... 

The chemistry of elements 104 through 106 has successfully been studied on this atom-at-a-time basis (see Refs. 11-14 for reviews). Recently, the chemistry of bohrimn (element 107) has been investigated for the first time by using an isothermal gas-phase system [15] and the first chemical studies of element 108 (hassium) have been reported [16]. Experiments with even heavier elements such as 112 [17] are imderway and others are planned as well. Complete overviews of the experimental procedures and results can be found in Ref. 46. 

The study of the chemical properties of the transactinide elements has been hampered by the short half-lives of many of the isotopes (the half-life of the longest known isotopes of the elements 106 and 107 are 21 s and 17 s, respectively, while those of 108 and 109 range from a few seconds down to milliseconds). In addition the production cross sections are very small (0.5 - 0.01 nb) so chemical studies must be done very rapidly on a few atoms at a time. However, these elements offer a fertile area to investigate the possibility of relativistic eflects of the electrons which could alter the relative stability of the 7s, 6d and 7p valence electrons. The result would be the existmice of the elemmits in oxidation states other than those predicted from their expected position in the periodic table, see App. I. 

The scale on which these transmutations is carried out is extremely small, and in some cases has been described as atom-at-a-time chemistry. The target materials in equations 3.22 and 3.23 are actinoid elements (see Chapter 25), which, although artificially prepared, have relatively long half-lives ( 9vBk, fi = 300 days geCm, h = 3.5 x 10 yr). Studying the product nuclides is extremely difficult, not only because of the tiny quantities of materials involved but also because of their short half-lives (losLr, t = 3 min lo Rf, ti = 65 s). 

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